>
>// The maximum AC potential across a blocking capacitor is typically
>less than a hundred volts at the lowest operating freq. The maximum DC
>potential across one is the no-load anode supply voltage. The critical
>rating is the RF ampere rating at the highest operating frequency. I see
>no reason for the ARRL's statement. QST no longer has a Technical
>Editor.
>
>In the 1999 ARRL Handbook (et al) on page 13.13, a formula is given
>as a "very rough rule of thumb" for figuring maximum RF current in a
>blocking capacitor @ 28 mhz. I "plugged in" 35pf anode C, 1 amp Ip,
>and 4 kv anode E. The result was 350 amps! (a bit high, me thinks!)
>Perhaps my ignorance of the "new math" caused an error????
>
// It ain't the math. I think this formula may have been from Dick
Ehrhorn. The current through the DC blocking C is a function of
anode-C, freq., and RMS anode V. DC anode current has nothing to do with
it. Where Dick got this nonsensical formula is a mystery.
cheers, Phil
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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